Problem: On Saturday, William's parents gave birth to twins and named them Omar and Brandon. When they were first born, Omar weighed 6.64 pounds, and Brandon weighed 8.89 pounds and was 20.5 inches tall. How much did the babies weigh in total?
Answer: To find the weights of the 2 babies, we need to add their weights together. Omar's weight + Brandon's weight = total weight. ${6}$ ${6}$ ${4}$ ${8}$ ${8}$ ${9}$ ${+\vphantom{0}}$ ${3}$ ${5}$ ${5}$ ${1}$ Together, the babies weigh 15.53 pounds.